The overall aim of the proposed Mentored Career Development Award (K01) is to provide me with intensive research career development training under the guidance of successful NIH-funded sponsors that will lead me to research independence. The proposed research study centers on elucidating the pathways to substance use among monoracial and biracial Black adolescents and young adults. Increasingly, substance use researchers refer to the catch-up effect to explain a paradoxical trend among Blacks in which lower rates of substance use in adolescence do not predict lower rates of substance use in adulthood. Although Black adolescents use substances at substantially lower rates than their White peers, by young adulthood the rates of substance use among Blacks catch up to or surpass the rates of Whites. This catch-up effect contributes to high rates of adverse social and health outcomes among Blacks. Understanding the catch-up effect is hindered by the normative practice of treating Blacks as a homogeneous group. Notably, as used for the US Census, Black includes African Americans, Africans, Afro- Caribbean's, and biracial Blacks-but without regard for different sociocultural experiences that might affect substance use. Thus, such aggregation likely obscures important between-group differences. Indeed, my preliminary research suggests a single substance use trajectory is wholly inadequate for either describing or predicting the pathways to substance use found among monoracial and various biracial Black subgroups. Excluding my preliminary findings, no research has examined predictors of substance use trajectories among de-aggregated samples of biracial Black youth. Hence, the proposed study seeks to address these knowledge gaps. It will reveal which subgroups are most vulnerable to the catch-up effect and which factors are critical determinants of substance use among monoracial and biracial Black subgroups during the transition from adolescence to young adulthood. This study proposes to use data obtained from two nationally representative studies: National Longitudinal Study of Adolescent Health (Add Health) and National Survey of American Life: Coping with Stress in the 21st Century (NSAL). This K01 seeks to 1) describe the developmental trajectories of cigarette, alcohol, and marijuana use among the monoracial groups (Black, Hispanic, and White) and two major biracial Black subgroups (Black-Hispanic, Black-White) during ages 11 to 34 years, which is a high-risk period for onset of substance use. Further, the K01 will 2) assess the relationships among socioeconomic status, experiences of racism, and individual/cultural, family, peer, school, and neighborhood factors and substance use (cross-sectional) and developmental trajectories of substance use (longitudinal) among monoracial and biracial Black adolescents and young adults. The proposed study is an integral component to a comprehensive training program designed to enhance my research skills; I have developed this program with the direction of an interdisciplinary team of expert mentors who will provide guidance throughout my K01 research. The proposed study advances my career goal of becoming a leading independent researcher focused on health disparities and the epidemiology, etiology, and prevention of substance use and dependence among racial/ethnic minorities, especially Black and biracial adolescents and young adults. My immediate career objectives in this K01 include developing greater expertise in developmental science, cultural factors, and health disparities; acquiring advanced methodological skills; conducting research that builds on my preliminary findings; disseminating my findings via peer- reviewed articles; presenting at national meetings; and preparing a grant application that will move my research to its next phase. I will achieve these goals by capitalizing on the exceptionally rich research environments at UNC and Duke University; acquiring knowledge through workshops, directed readings, and coursework; and conducting research under the guidance of my sponsors and advisors. The proposed research represents an unparalleled opportunity to develop an understanding of the pathways to substance use for specific biracial Black subgroups. Further, this research will contribute to the understanding of the etiology of substance use, the catch-up effect, and related health disparities among Blacks, and enhance prevention efforts. In the final stages of this K01, I will submit a R01 proposal that expands the scope of the investigation to examine the full range of de-aggregated biracial groups (e.g., American Indian-White, Asian-Hispanic) to determine whether, as suggested by some preliminary evidence, biracialism is a general risk factor for substance use behaviors or whether high risk for substance use is found among some biracial groups but not in others. In addition, the R01 study will examine concurrent and longer- term social and health correlates of substance use trajectories among biracial groups.